This present invention relates generally to wireless computer networking techniques. More particularly, the invention provides a method and a system for estimating the physical location of wireless transmitters in wireless networks according to a specific embodiment. Preferably the wireless transmitters are associated with certain undesirable wireless activity such as denial of service attacks, spoofing, address forging and others. Merely by way of example, the invention has been applied to a computer networking environment based upon the IEEE 802.11 family of standards, commonly called “WiFi.” But it would be recognized that the invention has a much broader range of applicability. For example, the invention can be applied to Ultra Wide Band (“UWB”), IEEE 802.16 commonly known as “WiMAX”, cellular wireless networks such as CDMA, GSM, GPRS, and others.
Computer systems have proliferated from academic and specialized science applications to day to day business, commerce, information distribution and home applications. Such systems include personal computers, which are often called “PCs” for short, to large mainframe and server class computers. Powerful mainframe and server class computers run specialized applications for banks, small and large companies, e-commerce vendors, and governments. Smaller personal computers can be found in many if not all offices, homes, and even local coffee shops. These computers interconnect with each other through computer communication networks based on packet switching technology such as the Internet protocol or IP. The computer systems located within a specific local geographic area such as an office, home or other indoor and outdoor premises interconnect using a Local Area Network, commonly called, LAN. Ethernet is by far the most popular networking technology for LANs. The LANs interconnect with each other using a Wide Area Network called “WAN” such as the Internet.
While conventional computer networks have proliferated in the past, wireless communication technologies are currently increasing in popularity. That is, wireless communication technologies wirelessly connect users to the computer networks. Examples of wireless networks include, but are not limited to, wireless local area networks (WLAN) and cellular networks. One desirable application of wireless networks is to provide wireless access to the LAN in the office, the home, public hot-spots, and other geographical locations. As merely an example, the IEEE 802.11 family of standards, commonly called WiFi, is the common standard for such wireless applications. Among WiFi, the 802.11b standard-based WiFi often operates at the 2.4
GHz unlicensed radio frequency spectrum and offers wireless connectivity at speeds up to 11 Mbps. The 802.11g compliant WiFi offers even faster connectivity at about 54 Mbps and operates at the 2.4 GHz unlicensed radio frequency spectrum. The 802.11a standard provides speeds up to 54 Mbps operating in the 5 GHz unlicensed radio frequency spectrum. WiFi enables a quick and effective way of providing wireless extension to the existing LAN.
In order to provide wireless extension of the LAN using WiFi, one or more WiFi access points (APs) connect to the LAN connection ports either directly or through intermediate equipment such as a WiFi switch. A user can wirelessly connects to the LAN using a device equipped with a WiFi radio, commonly called a wireless station that communicates with the AP. The connection is free from cable and other physical encumbrances and allows the user to “Surf the Web,” check e-mail, or use enterprise and e-commerce computer applications in an easy and efficient manner. Since access points have limited signal coverage, multiple access points may be required to provide signal coverage throughout a facility. Another advantage of wireless networks is that wireless stations can move throughout the signal coverage area and continue to connect to the computer network. In a typical operational wireless network, multiple wireless stations operate from different locations within the geographic area comprising the wireless network. Station locations may also change from time to time as the users carrying those devices move.
Determining the physical location of a wireless station, or that of a signal transmitting device, is useful for many applications, such as dispatching and location based applications. Physical location information regarding a wireless station is critical if said station either deliberately or unknowingly is causing harm to the wireless network in the form of a security breach, intrusion, performance degradation, and the like. Knowing the physical location of the wireless station in these scenarios enables the network administrator to track down the station and take action (e.g., remove it from the vicinity of the network) to avoid a security or performance catastrophe. However, location tracking capability is often not supported by standard WiFi communication systems and hence a location tracking solution is highly desirable.
Prior solutions have attempted to provide mechanisms to determine the physical location of a wireless station, with varying degrees of success. One conventional technique for location determination in local area wireless networking environments involves triangulating the position of the wireless station with respect to predetermined reference locations, based on signal strength measurements. A number of wireless access points or sniffers are provided at reference locations in the region of operation of the local area network. These access points or sniffer devices measure the received signal strength from the transmitting wireless station. The signal measurements of various access points or sniffer devices are collected at a server and the physical location of the station triangulated. Certain factors such as the layout of the region (e.g., walls, doors, roof, and other components that cause signal attenuation and/or reflection) and the statistical variability of the received signal strength can also be considered during triangulation.
Another conventional technique for location determination in local area wireless networking environments involves definition of areas within the geographic region of interest. A signal strength signature is then created for each area, representing the received signal strength measured at one or more network access points or sniffers and originating from the device transmitting from the area. During the operation, the area in which a transmitting wireless station resides is determined by comparing with the signal strength signature for various areas, the observed received signal strengths from the transmitting wireless station received at the network access points or sniffers. The comparison can be done via pattern matching.
These prior art techniques are not able to provide solutions for determining the physical location of wireless stations associated with certain undesirable wireless activities, such as certain denial of service (DOS) attacks, identity theft (e.g., spoofing), address forging, and the like. These and other limitations are described throughout the present invention. Accordingly, there is need in the art for techniques and systems for determining (estimating) the location of wireless stations associated with certain undesirable wireless activities.